Method of forming passages in a forgewelded sheet metal structure



ORN 2,756,487

IN A FORGEWELDED W2 5 C9 U l @R DGS 8 Mn u EJ M m l 5 F S July 31, 1956 J. H. HEI METHOD OF FORMING PASSA M1 a. c C I t I z T u T T T .u u r u. u. t I I Z L u" rm fi Z ,fillxxllt lllzllll munununul nuunn HE INVENTOR.

United States Patent ll/IETHOD OF FORMING PASSAGES IN A FORGE- WELDED SHEET METAL STRUCTURE John H. Heidorn, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application June 4, 1952, Serial No. 291,634

3 Claims. (Cl. 29-1573) This invention relates to refrigerating apparatus and more particularly to an improved form of evaporator and the method of making the same.

It has been found practical to manufacture plate type evaporators by a roll forging process wherein two superimposed sheets of metal are forge welded together on their meeting faces at all points except where a vein of stop-weld material has been provided between the sheets prior to the forge welding operation. This process presents problems when it comes to the matter of attaching conduits to the evaporator. One of the primary objects of this invention is to provide an improved method of making connections to the evaporator in a manner to avoid the introduction of chips into the interior of the evaporator.

Another object of this invention is to provide a construction which eliminates the need for making the connections at the edges of the force welded sheets.

Still another object of this invention is to provide a method whereby the refrigerant lines are connected to the plate while it is still perfectly flat.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Figure 1 is a plan view of a roll forged heat exchanger prior to the attachment of any refrigerant lines and prior to the dilation of the internal passages;

Figure 2 is a fragmentary elevational view showing an intermediate step in the manufacture of the evaporator;

Figure 3 is a fragmentary sectional view taken substantially on line 33 of Figure 2;

Figure 4 is a vertical sectional view showing the evaporator held between the pair of substantially flat plates during the process of dilating the refrigerant passages;

Figure 5 is a fragmentary sectional view similar to Figure 3 but showing the evaporator after the refrigerant passages have been dilated; and

Figure 6 is a fragmentary sectional view showing a modified form of refrigerant connection.

For purposes of illustrating the invention, there is shown a fiat plate evaporator of the type used in the main food storage compartment of a conventional household refrigerator whereas the invention is equally applicable to other types of heat exchanger units such as condensers, radiators and the like.

Referring now to the drawing, reference numeral 10 designates a roll forged plate type evaporator which is made by superimposing one sheet upon the other with a stop-weld material provided between the sheets in a predetermined pattern such as that indicated by the reference numeral 12. The pattern determines the shape and location of the passages formed in the evaporator. The stop-weld material may be applied in any manner such as by printing, rolling, painting or spraying and is in the form of a water suspension of colloidal graphite and sodium silicate which serves as a binder. These plates "ice may be made of copper, aluminum, bronze or any other type of material which is capable of being roll forged.

During the roll forging operation the plates are heated and passed between rollers which reduce the thickness of the plates and cause them to become welded together except throughout the area covered by the stop-weld material 12. When the plates are removed from the rollers they are perfectly flat on both sides without any internal passages.

The internal passages are formed by introducing a fluid or liquid which hydraulically separates the plates throughout the area covered by the stop-weld material. In order to introduce the fluid between the plates it is necessary to make some connection to the interior of the plates. In making this connection it is important to prevent the introduction of any metal ships or other foreign matter into the evaporator. In the past it has been customary to apply the stop-weld material in such a manner that at one or more points the stopweld material extends all the way to the edge of the plates and to mechanically force the plates apart at the edge where the stop-weld material is exposed and to then insert a tube which is brazed or otherwise welded to the plates so as to allow for the introduction of a fluid for dilating the plates. This procedure necessitates placing the conduit at the edge of the evaporator plate whereas it is seldom desirable to make the connection at the edge of the plate.

I have discovered that the preferred arrangement for making a connection to the interior of the plate is by counterboring the one side of the plate by means of a conventional drill or counterboring element 16. The lower end of the drill 16 has been shown broken away in Figure 3 so as to expose the stop-weld material 12. This counterbore 14 is made at the particular point where it is desired to make connection to the evaporator and is made before the plate is dilated, with the result that no chips can possibly enter the interior passages of the evaporator as these passages are still closed.

The depth of the counterbore should be just enough to reach the vein of stop-weld material 12. A short conduit or tube 18 is then inert gas welded or otherwise secured to the face of the plate 10 at the point of the counterbore so as to make connection to the interior of the plate. Any chips or loose flux may readily be cleaned out of the tube section and the counterbore by means of a. blast of compressed air or the like. The tube section 18 provides a convenient means for supplying fluid into the evaporator for dilating the passages therein.

While I have described the attachment of the conduit 18 after making the counterbore 14, it is within the purview of this invention to attach the conduit 18 to the face of the plate before counterboring the plate. In this latter case the drill 16 would be inserted down through the conduit 18 and in either case the conduit is attached before the refrigerant passages are dilated.

As indicated by Figure 4 of the drawing the plate 10 is placed between a pair of relatively heavy plates or blocks 24 during the process of dilating the internal passages within plate 10. The plates or blocks 24 serve to limit the extent of dilation which takes place and also serves to keep the plates from warping when the passages are being dilated.

As shown in Figure 4 of the drawing, the one block 24 is provided with an integral extension 26 which is adapted to press against the flange 30 provided on the lower end of the conduit 18 so as to prevent excessive strain on the welded joint 20 between the tube 18 and the plate 10. While this latter feature has been used as a precautionary feature it could be omitted in which case the extra strength of the flange 30 would be depended upon to prevent excessive strain on the welded joint. One could omit the projection 26 in which case the fluid used 101 dilating the. passage might tend to cause a certain amount of distortion of the flange 30 directly above the point where the stop-weld material occurs, but any tendency to cause injurious distortion could be prevented by providing a strong welded'joint and by suitably controlling the pressures used in dilating the sheet.

As indicated in Figure 6 of the drawing, the conduit which is attached to the plate 10 need not be perpendicular to the side of the evaporator. It may take most any shape or it may be straight to begin with and then bent so as to lie at an angle to the surface of the plate as indicated by Figure 6 of the drawing.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. The process of forming a single sheet of metal having within its interior a passageway of predetermined coufiguration which consists in superimposing one upon the other two weldable sheets of metal having therebetween a stop-weld material arranged in the configuration of the desired passageway, forge welding the two sheets by hot rolling thetwo sheets into a single composite sheet of greater length and less thickness, counterboring through the one side of said composite sheet tothe depth of said stop-weld material after said forge welding, attaching a tube to said one side in alignment with said counterbore and thereafter expanding the sheet to form said passageway by applying fluid pressure through said tubing.

2. The process of forming passages in a forge welded sheet metal structure having undilated veins of stop-weld material between outer layers of sheet metal and providing a potential passageway which comprises, counterbor- 4 ing through one side of the forge welded structure to a suffcient depth to reach said stop-weld material, attaching a tube to said one side in alignment with said counterbore and thereafter applying a sufiiciently high fluid pressure through said tube to within the vein to dilate the same.

3. The process of forming a single sheet of metal having within its interior a passageway of predetermined configuration which consists in superimposing one upon the other two weldable sheets of metal having therebetween a stop-weld material arranged in the configuration of the desired passageway, forge welding the two sheets by hot rolling the two sheets into a single sheet of greater length and less thickness, counterboring through the one side of said final sheet to a sufiicient depth to reach said stop-weld material, attaching a tube to said one side in alignment with said counterbore and thereafter expanding the sheet between opposite spaced substantially parallel rigid surfaces by applying hydraulic pressure'within the space occupied by the stop-weld material until the sheet portions adjacent the stop-weld material are forced into extended flat contact with the parallel surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 29,276 Holmes July 24, 1860 1,709,865 Muftly Apr. 23, 1929 1,994,903 Warrender Mar. 19, 1935 2,212,481 Sendzimir Aug. 20, 1940' 2,662,273 Long Dec. 15, 1953 FOREIGN PATENTS 401,276 Germany Sept. 8, 1924 

1. THE PROCESS OF FORMING A SINGLE SHEET OF METAL HAVING WITHIN ITS INTERIOR A PASSAGEWAY OF PREDETERMINED CONFIGURATION WHICH CONSISTS IN SUPERIMPOSING ONE UPON THE OTHER TWO WELDABLE SHEETS OF METAL HAVING THEREBETWEEN A STOP-WELD MATERIAL ARRANGED IN THE CONFIGURATION OF THE DESIRED PASSAGEWAY, FORGE WELDING THE TWO SHEETS BY HOT ROLLING THE TWO SHEETS INTO A SINGLE COMPOSITE SHEET OF GREATER LENGTH AND LESS THICKNESS, COUNTERBORING THROUGH THE ONE SIDE OF SAID COMPOSITE SHEET TO THE DEPTH OF SAID STOP-WELD MATERIAL AFTER SAID FORGE WELDING, ATTACHING A TUBE TO SAID ONE SIDE IN ALIGNMENT WITH SAID COUNTERBORE AND THEREAFTER EXPANDING THE SHEET TO FORM SAID PASSAGEWAY BY APPLYING FLUID PRESSURE THROUGH SAID TUBING. 